Does it account for Daylight Saving Time?

Yes, our converter uses the IANA timezone database, which includes all current DST rules for every timezone in the world.

UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks. All timezones are defined as offsets from UTC.

Can I compare multiple timezones at once?

Yes, you can add multiple cities or timezones and see the equivalent times side by side.

How many timezones are there in the world?

There are 38 distinct UTC offsets in use, ranging from UTC-12 to UTC+14. This includes half-hour (UTC+5:30 India, UTC+9:30 Australia) and 45-minute offsets (UTC+5:45 Nepal, UTC+8:45 Australia).

What is the International Date Line?

The International Date Line (IDL) runs roughly along the 180° meridian in the Pacific Ocean. When you cross it westward, you gain a day; crossing eastward, you lose a day.

Why do some timezones have 30 or 45 minute offsets?

Countries chose offsets that best matched their solar noon. India uses UTC+5:30 and Nepal uses UTC+5:45 because standard hourly offsets didn't align well with their geography.

Which country has the most timezones?

France has the most (12 timezones) due to overseas territories. Russia spans 11 timezones. The US has 6 (including Hawaii and Alaska).

IRST to CDT

-8h 30m

IRST

IRSTSOURCE

UTC+03:30

HH12

MM00

12:00 (24-hr)

12 AM6 AM12 PM6 PM12 AM

CDT

UTC-05:00☀ DST active

HH03

MM30

03:30 (24-hr)

12 AM6 AM12 PM6 PM12 AM

Quick Reference

Time Conversion Table

IRST

CDT

12:00 AM

3:30 PM-1

2:00 AM

5:30 PM-1

4:00 AM

7:30 PM-1

6:00 AM

9:30 PM-1

8:00 AM

11:30 PM-1

10:00 AM

1:30 AM

12:00 PM

3:30 AM

2:00 PM

5:30 AM

4:00 PM

7:30 AM

6:00 PM

9:30 AM

8:00 PM

11:30 AM

10:00 PM

1:30 PM

Green rows indicate typical business hours (9 AM - 5 PM)

IRST and CDT on the World Map

The map below highlights the IRST (Iran Standard Time) and CDT (Central Daylight Time) timezone regions across the globe.

IRST Zone

→

CDT Zone

Explore all world timezones interactively →

IRST – Iran Standard Time

UTC+03:30

Iran Standard Time (IRST) is the time zone for Iran, 3 hours and 30 minutes ahead of UTC.

Countries in IRST

Iran

Major Cities in IRST

TehranIsfahanMashhadTabrizShirazKaraj

Key Facts about IRST

•IRST is one of only a few time zones with a 30-minute offset.
•Iran observes daylight saving time, switching to IRDT (UTC+04:30).
•Tehran has a metropolitan population of over 16 million.

Daylight Saving:Yes – switches to IRDT

Learn more about IRST on Wikipedia

CDT – Central Daylight Time

UTC-05:00

Central Daylight Time (CDT) is the daylight saving offset in the Central Time Zone, 5 hours behind UTC.

Countries in CDT

United States (Central)Canada (Manitoba)

Major Cities in CDT

ChicagoHoustonDallasAustinWinnipegNashville

Key Facts about CDT

•CDT is the same offset as EST (UTC-05:00), which can cause confusion.
•CDT runs from the second Sunday in March to the first Sunday in November.

Daylight Saving:Yes – switches to CST

Learn more about CDT on Wikipedia

Everything You Need to Know About IRST and CDT Time

IRST runs on Iran Standard Time (IRST) at UTC+03:30. CDT runs on Central Daylight Time (CDT) at UTC-05:00. That puts IRST 8 hours 30 minutes behind CDT — a difference of -8h 30m at the current offsets.

In practice, when it is 9:00 AM in IRST it is 12:30 AM in CDT. Midnight in IRST is 3:30 PM in CDT. Neither zone observes daylight saving time, so the offset between them stays constant all year.

IRST to CDT time conversion table

IRST (IRST)	CDT (CDT)	Day
12:00 AM	3:30 PM	previous day
6:00 AM	9:30 PM	previous day
7:00 AM	10:30 PM	previous day
8:00 AM	11:30 PM	previous day
9:00 AM	12:30 AM	same day
12:00 PM	3:30 AM	same day
3:00 PM	6:30 AM	same day
5:00 PM	8:30 AM	same day
6:00 PM	9:30 AM	same day
9:00 PM	12:30 PM	same day

Why people convert IRST to CDT time

Scheduling a call from IRST to CDT: a 10:00 AM start in IRST lands at 1:30 AM in CDT, so you can confirm the slot without doing the arithmetic yourself.
Handling a -8h 30m gap: IRST and CDT have no overlap inside a normal 9-to-5 day, so real-time meetings need an early-morning or late-evening slot on one side. 9:00 AM in CDT is 12:30 AM in IRST.
Booking travel or deliveries: tracking CDT local time against IRST keeps pickup windows and arrival estimates honest across the -8h 30m offset.

Always state the zone abbreviation, not just the hour. "3:00 PM IRST" is unambiguous; "3 PM" across a -8h 30m gap is not.
With a -8h 30m gap there is no shared 9-to-5 window, so alternate the early start: one week IRST takes the early slot, the next week CDT does.

About IRST (Iran Standard Time)

Iran Standard Time (IRST) is one of the few time zones with a 30-minute offset. Iran observes daylight saving time (IRDT, UTC+04:30) from late March to late September. Tehran, the capital, is one of the largest cities in the Middle East.

About CDT (Central Daylight Time)

Central Daylight Time (CDT) is observed during summer months in the US and Canadian portions of the Central Time Zone. Clocks are moved forward by one hour, aligning with Eastern Standard Time (EST). Most of Mexico and Central America do not observe CDT, staying on CST year-round.

Best time to call between IRST and CDT

With a -8h 30m offset there is no overlap inside a normal 9 AM – 5 PM day. CDT opens at 9:00 AM CDT, which is 12:30 AM in IRST, so real-time calls need an early-morning or late-evening slot on one side.

Business hours overlap

IRST and CDT have no shared working hours because of the -8h 30m gap. Teams need to alternate early starts or rely on asynchronous handovers.

IRST is 8 hours 30 minutes behind CDT (IRST UTC+03:30 → CDT UTC-05:00). There is no shared 9-to-5 window, so plan around an early or late slot. Remember to re-check around daylight-saving transitions.

🕐 Daylight Saving Time Info

IRST

Does not observe DST

CDT

☀ Currently in DST

Standard: UTC-06:00 · DST: UTC-05:00

Clocks fall back on Sun, Nov 1, 2026

Learn More About Time

Dive deeper into the fascinating world of timekeeping, time zones, and how they shape our global society:

⏳

History of Timekeeping

From sundials to atomic clocks - 5000 years of measuring time

🌍

How Time Zones Work

UTC, offsets, and why zones don't follow straight lines

☀️

Daylight Saving Time

DST dates, which countries observe it, and the ongoing debate

Frequently Asked Questions

What is the time difference between IRST and CDT?

IRST (IRST, UTC+03:30) is 8 hours 30 minutes behind CDT (CDT, UTC-05:00). The gap is currently -8h 30m.

How do I convert IRST time to CDT time?

Add -8h 30m to IRST local time. For example, 9:00 AM in IRST is 12:30 AM in CDT.

What time is it in CDT right now?

CDT uses CDT at UTC-05:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -8h 30m offset from IRST.